James Taranto notes that gays aren't responsible for the decline of marriage.
Deroy Murdock made a good point some years back when he observed, in a column posted at NRO, that "social conservatives who blow their stacks over homosexual matrimony's supposed threat to traditional marriage tomorrow should focus on the far greater damage that heterosexuals are wreaking on that venerable institution today."
Murdock should have written "have wreaked for decades," because the developments we note all long predate any serious consideration of the idea of same-sex marriage. And it must be said that some social conservatives--notably Maggie Gallagher, another frequent National Review contributor--do take a broader view of the subject. As a political matter, however, outside the area of abortion it is hard to find a constituency whose members are eager to subject themselves to greater obligations or constraints in the name of social stability or for the good of the next generation.
Thus for the foreseeable future, civil marriage is likely to retain its character as little more than a financial arrangement. To be sure, many individual marriages are deeply committed relationships. But under a regime that permits either spouse to opt out of the commitment at will, the legal recognition of marriage is mere symbolism.
The people most responsible for the decline of marriage as an institution are the divorced people who didn't value their own marriages.